docs: def generate_report(book_url):
      """
      Generates the report HTML.
      """
      with piecash.open_book(book_url, readonly=True, open_if_lock=True) as book:
          accounts = [acc.fullname for acc in book.accounts]
  
          return f"""<html>
          <body>
              Hello world from python !<br>
              Book : {book_url}<br>
              List of accounts : {accounts}
          </body>
          </html>"""